John Gruber has found out that cross-compilers are no longer allowed in iPhone OS 4.0. "My reading of this new language is that cross-compilers, such as the Flash-to-iPhone compiler in Adobe's upcoming Flash Professional CS5 release, are prohibited. This also bans apps compiled using MonoTouch - a tool that compiles C# and .NET apps to the iPhone. It's unclear what this means for tools like Titanium and PhoneGap, which let developers write JavaScript code that runs in WebKit inside a native iPhone app wrapper. They might be OK."

Microsoft, like any other publisher in the games industry has the right to decide which games they want to publish on their platform. This is a rule well known in the games industry and happens all the time.

What Apple is doing on the other hand, is completely different! They are changing the rules in the middle of the game, about which languages you are allowed to use for their platform.